Fatigue

Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. It is important to consider fatigue during design as stress values that cause fatigue damage are much less than the yield strength of the material.

Challenges

More and more wells and surrounding equipments are subject to fatigue loads during the different phases of the well life (drilling, production, work-over). This is especially true as wells are being drilled in more challenging environment and within increasing water depth.

  • Shale gas / Horizontal wells: horizontal wells require rotation to run casing
  • Extended Reach Drilling: friction loads are so important that the casing need to rotate during running, cementation... 
  • Drilling with Casing may be required to drill thru unstable formation or when drilling loss are too important.

In each case, fatigue resistance must be determined as rotation in the bend will necessarily generate fatigue loading on the casing

  • Top Tension Risers: used within significant water depth (5000ft and more) requires the evaluation of the OCTG risers to make sure they exhibit enough fatigue resistance against the currents and wave.

Solutions

To be able to provide answers to these challenges, constant development of products, testing, manufacturing and services has been ongoing within Vallourec including:

  • Full-scale fatigue testing of the VAM® OCTG family to determine resistance to fatigue of each product.
  • Assessment of the impact of fatigue on other critical product functions such as sealability, mechanical resistance after fatigue.
  • Assessment of the combined effects of corrosion and fatigue.
  • Development of FEA methodologies to assess the fatigue performance.
  • Development of VAM® OCTG products with superior resistance to fatigue for applications such as Drilling with ​Casing or dry tree risers.
  • Development of material specially designed for fatigue applications including e.g. CTOD guaranteed values.
  • Material & Connection​ selection for fatigue applications.
  • VAM® licensee network close to customers' operations
  • Worldwide network of VAM®  Fiel​d Service making sure pipes are run properly.